JPH1063914A - Device for inspecting paper sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly discriminate the validity of a paper sheet even when any paper sheet deviation is generated. SOLUTION: A paper sheet 1 is irradiated with a band-shaped light 20a before the paper sheet 1 is inputted to a scanning optical system, a light quantity corresponding to the attitude of the paper sheet 1 among the irradiated light quantity is detected by a shift value sensor 21, and the horizontal deviation value S and inclination θ of the paper sheet 1 are calculated. Reference data are corrected based on those deviation value S and inclination θ, and the validity of the paper sheet 1 is discriminated based on actual data corresponding to the light quantity of a transmitted light and a reflected light from the paper sheet 1 when a light is scanned for the paper sheet 1 and the corrected reference data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper sheet inspection apparatus which receives transmitted light and reflected light when light is applied to a paper sheet to determine whether the watermark of the paper sheet is good or not.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of a paper sheet inspection apparatus. A plurality of laser oscillators 3, for example, semiconductor lasers, are arranged in the transport line 2 of the paper sheet 1 above the transport line 2 in a direction perpendicular to the transport direction (A). Note that a plurality of laser oscillators 4 such as semiconductor lasers are also arranged below the transport line 2 in a direction perpendicular to the transport direction (a).

On the other hand, a plurality of light receiving sensors 5a are provided below the transport line 2 so as to face the respective positions of the laser oscillators 3.
Are arranged, and obliquely below from the transport line 2,
A plurality of light receiving sensors 6a are arranged corresponding to respective arrangement positions of the respective laser oscillators 4.

[0004] One of the light receiving sensors 5a receives laser light emitted from each laser oscillator 3 and transmitted through the paper sheet 1, and outputs an electric signal corresponding to the light amount. Each of the other light receiving sensors 6a receives the reflected scattered light when the laser light is emitted from the laser oscillator 4 to the paper sheet 1, and outputs an electric signal corresponding to the light amount.

A plurality of light-receiving sensors 5b are arranged above the transport line 2 corresponding to the respective positions of the laser oscillators 4, and a plurality of light-receiving sensors 5b are obliquely above the transport line 2. 6b are arranged corresponding to the respective arrangement positions of the respective laser oscillators 3.

Each of the light receiving sensors 5b receives the laser light emitted from the laser oscillator 4 and transmitted through the paper sheet 1, and outputs an electric signal corresponding to the light amount. The sensor 6b receives reflected light from the paper sheet 1 when each of the paper sheets 1 is irradiated with each laser beam from the laser oscillator 3, and outputs each electric signal according to the amount of received light. is there.

The light receiving sensors 5a, 5b, 6
The output terminals of a and 6b are the amplifiers 8 respectively.
Through 11 are connected to the discriminating device. With such a configuration, when the paper sheet 1 is conveyed to the conveyance line 2 at a constant speed, the paper sheet 1 passes below the laser oscillators 3 so that the paper sheets 1 Each output laser beam is scanned.

[0008] The spot shape of each of the scanned laser beams on the paper 1 is dot-shaped, and these laser beams pass through the paper 1 and are reflected by the paper 1.
At the same time, by passing above the laser oscillator 4, each of the laser beams output from each of the laser oscillators 4 is scanned on the sheet 1.

The spot shape of each of the scanned laser beams on the paper 1 is dot-shaped, and these laser beams are transmitted through the paper 1 and reflected by the paper 1.
At this time, each lower light receiving sensor 5a receives each laser beam output from each laser oscillator 3 and transmitted through the paper sheet 1, and outputs each electric signal according to the light amount. The light receiving sensor 6b receives the reflected scattered light when the paper sheet 1 is irradiated with the laser light, and outputs each electric signal corresponding to the light amount.

At the same time, each upper light receiving sensor 5a
Each laser beam output from each laser oscillator 4 and transmitted through the paper sheet 1 is received, and each electric signal corresponding to the light amount is output.
, Respectively, receives the reflected scattered light when the laser light is irradiated, and outputs each electric signal corresponding to the light amount.

The light receiving sensors 5a, 5b, 6a, 6b
Are amplified by the amplifiers 8 to 11 and sent to the discriminating device. This discriminating device is a transmission light distribution for each scanning line when each of the laser beams output from each of the laser oscillators 3 and 4 is scanned on the paper sheet 1 being conveyed. , The reflected light distribution is stored as reference data, and when each electric signal from each of the light receiving sensors 5a, 5b, 6a, 6b is input, the measured data for each scanning line from these electric signals, that is, the transmitted light distribution, reflected light The light distributions are obtained, and these distributions are compared with the transmitted light distribution and the reflected light distribution of the reference data to determine the quality of the paper sheet 1.

[0012]

However, on the transport line 2, the paper sheet 1 is not transported in a normal posture as shown in FIG. In some cases, the sheet may be conveyed after being laterally displaced, inclined as shown in FIG. 14, or both laterally displaced and inclined.

When the sheet is conveyed with such a sheet shift, the actual scanning line for the sheet 1 is deviated from the scanning line for the sheet 1 when conveyed in a normal posture. Becomes

For this reason, the reference data stored in the discriminating device is a transmitted light distribution and a reflected light distribution when the sheet 1 is conveyed in a normal posture, and the reference data is shifted from the scanning line. Even if it is compared with the actually measured data, accurate pass / fail judgment cannot be obtained, and the reliability of the pass / fail judgment result decreases.

In order to cope with such a sheet deviation, there is a technique of forming a scanning spot of a laser beam in a linear or elliptical shape. This is because a linear or elliptical laser spot is irradiated on the paper sheet 1, the transmitted light and the reflected light are received, and the transmitted light distribution or the reflected light distribution in the major axis direction of the ellipse is averaged to some extent. The effect of the occurrence of lateral displacement of class 1 is minimized.

However, since the transmitted light distribution or the reflected light distribution in the direction of the major axis of the ellipse is averaged to some extent, the criteria for judging the quality of the paper sheet 1 are relaxed, and, for example, the ability to remove defective products is tolerated. And it becomes difficult to eliminate defective products with a high probability. Therefore, the present invention
It is an object of the present invention to provide a sheet inspection apparatus capable of accurately determining the quality of a sheet even if a sheet shift occurs.

[0017]

According to the first aspect of the present invention, light is scanned on a conveyed paper sheet, and measured data and reference data corresponding to the amount of transmitted light or reflected light from the paper sheet. In a sheet inspection apparatus for inspecting the quality of sheets based on the posture detection means for detecting the posture of the conveyed paper sheets, based on the posture of the paper sheets detected by the posture detection means Reference data correction means for correcting the reference data by
A sheet inspection apparatus comprising: reference data corrected by the reference data correction means; and actual measurement data to determine whether the paper is good or bad.

In such a sheet inspection apparatus, the posture of the conveyed sheet is detected, and the reference data is corrected based on the posture of the sheet. Then, light is scanned on the conveyed paper sheet, and the quality of the paper sheet is inspected based on the actually measured data corresponding to the amount of transmitted light or reflected light from the paper sheet and the corrected reference data. I do.

According to a second aspect of the present invention, in the paper sheet inspection apparatus according to the first aspect, the posture detecting means is disposed at a stage preceding the scanning optical system that scans the paper sheet with light. With such a paper sheet inspection apparatus, before scanning the paper sheet with light, the posture of the paper sheet is detected and the reference data is corrected, and then the light is scanned on the paper sheet. Then, the quality of the paper sheet is inspected based on the measured data according to the amount of transmitted light or reflected light from the paper sheet and the corrected reference data.

According to a third aspect of the present invention, in the paper sheet inspection apparatus according to the first aspect, the posture detecting means includes: a light source for irradiating the sheet with a band-shaped light; A shift amount sensor that detects a light amount corresponding to the posture of the leaves, and a posture estimating unit that calculates a lateral shift amount and a tilt of the paper sheet based on the light amount detected by the shift amount sensor;
Having.

In such a paper sheet inspection apparatus, the posture of the paper sheet at the time of conveyance is such that a belt-like light is applied to the paper sheet, and the posture of the paper sheet depends on the posture of the paper sheet out of the irradiated light amount. The detected light amount is obtained, and the lateral shift amount and inclination of the paper sheet are obtained based on the detected light amount.

According to a fourth aspect of the present invention, in the paper sheet inspection apparatus according to the third aspect, the posture estimating means determines that the change in the amount of light detected by the shift amount sensor is temporally constant outside the allowable range. It has a function of obtaining the lateral shift amount of the paper sheet from the light amount at this time, and calculating the inclination of the paper sheet from the rate of change in the light amount at this time if the light amount detected by the shift amount sensor increases or decreases with time.

With such a paper sheet inspection apparatus, the posture of the paper sheet at the time of conveyance is detected by irradiating a belt-like light to the paper sheet and detecting the amount of light corresponding to the posture of the paper sheet. If the change in the light amount is temporally constant outside the allowable range, the lateral deviation amount of the paper sheet is obtained from the light amount at this time, and if the light amount increases or decreases over time, the paper sheet is calculated from the rate of the light amount change at this time. Find the slope of the class.

According to a fifth aspect of the present invention, in the sheet inspection apparatus according to the first aspect, each of the transmission light distributions or the reflection light distributions corresponding to each scanning position when the paper sheet is transported in a normal posture. Either or both are held as reference data, and the reference data correction means obtains the actual scan line position based on the lateral shift amount and inclination of the sheet, and transmits the actual scan line position on the reference data corresponding to this scan line position. It has a function of extracting the light amount or the reflected light amount and generating reference data corresponding to the posture of the paper sheet.

In such a paper sheet inspection apparatus, for example, a belt-like light is applied to the paper sheet to detect a light amount corresponding to the posture of the paper sheet, and the lateral displacement of the paper sheet is determined based on this light amount. When the amount and the inclination are obtained, the actual scanning line position on the sheet is obtained based on the lateral deviation amount and the inclination, and the transmitted light amount or the reflected light amount on the reference data corresponding to this scanning line position is taken out to obtain the sheet amount. Generate reference data corresponding to the posture of the object.

According to a sixth aspect of the present invention, in the paper sheet inspection apparatus according to the first aspect, the determining means obtains a Mahalanobis distance based on an average value and a standard deviation between the corrected reference data and the actually measured data. It has a function of comparing the Mahalanobis distance with a threshold to determine the quality of the paper sheet.

With such a paper sheet inspection apparatus, the posture of the conveyed paper sheet is detected, the reference data is corrected based on the posture of the conveyed paper sheet, and the subsequently conveyed paper sheet is detected. Scanning the light to obtain measured data according to the amount of transmitted light or reflected light from the paper sheet, the Mahalanobis distance based on the average value or standard deviation between the corrected reference data and the measured data Is calculated, and the Mahalanobis distance is compared with a threshold value to determine the quality of the paper sheet.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 11 are denoted by the same reference numerals. FIG. 1 is a configuration diagram of a paper sheet inspection apparatus.

In the transport line 2, a plurality of laser oscillators 3, for example, semiconductor lasers, are arranged above the transport line 2 in a direction perpendicular to the transport direction (a). A plurality of laser oscillators 4 such as semiconductor lasers are also arranged below the transport line 2 in a direction perpendicular to the transport direction (A).

On the other hand, a plurality of light receiving sensors 5a are provided below the transport line 2 so as to face the respective positions of the laser oscillators 3.
Are arranged, and obliquely below from the transport line 2,
A plurality of light receiving sensors 6a are arranged corresponding to respective arrangement positions of the respective laser oscillators 4.

A plurality of light receiving sensors 5b are arranged above the transport line 2 corresponding to the respective positions of the laser oscillators 4, and a plurality of light receiving sensors 5b are obliquely above the transport line 2. 6b are arranged corresponding to the respective arrangement positions of the respective laser oscillators 3.

The light receiving sensors 5a, 5b, 6
The output terminals of a and 6b are the amplifiers 8 respectively.
To 11 are connected. On such a transport line 1, in front of the scanning optical system, a slit light source 20 and a shift amount sensor 21 constituting an attitude detecting unit are provided as shown in FIG.
As shown in FIG.

The slit light source 20 is a band-like light 20a in a direction perpendicular to the conveying direction (a) of the paper sheet 1 in a normal posture.
It radiates. The shift amount sensor 21 receives the band-shaped light 20a emitted from the slit light source 20 and not shielded by the paper sheet 1, as shown in the characteristic diagram of the incident light amount-output voltage of the shift amount sensor 21 in FIG. Has a function of outputting a voltage V proportional to the amount of incident light I.

That is, the shift amount sensor 21 outputs the output voltage V according to the lateral shift amount and the inclination amount of the paper sheet 1 since the incident light amount I varies according to the lateral deviation amount and the inclination amount of the paper sheet 1. Gain. Here, assuming that the lateral shift amount of the paper sheet 1 is S,

[0035]

(Equation 1) Therefore, the following relationship is obtained: V = f (as) (2)

FIG. 4 is a block diagram of the discrimination processing system.
Each of the A / D converters 3 is provided in a main control unit 30 including a CPU and the like.
1, 32, each shift amount data memory 33, an actual measurement data memory 34, and a reference data memory 35 are connected.
A posture estimating unit 36, a reference data correcting unit 37, a comparing unit 38, and a pass / fail determination unit 39 are operated by a command issued from the main control unit 30.

Of these, one A / D converter 31 has:
Each light receiving sensor 5 via each amplifier 8 to 11
a, 5b, 6a, and 6b are connected, and the shift amount sensor 21 is connected to the other A / D converter 32.

The shift amount data memory 33 converts the output voltage V of the shift amount sensor 21 into digital data and stores it as posture data of the paper sheet 1. Measurement data memory 3
4, each electric signal output from each of the light receiving sensors 5a, 5b, 6a, and 6b is converted into a digital signal,
Amplitude data of reflected light distribution (hereinafter referred to as measured data)
Is stored as

In the reference data memory 35, one or both of the transmitted light distribution and the reflected light distribution corresponding to each scanning position by each laser beam when the sheet 1 is conveyed in a normal posture is referred to. It is stored as data D _s.

[0040] The reference data D _s, for example the scanning lines s ₁ as shown in FIG. 5, s _2, ... s each amplitude data D of the transmitted light distribution or distribution of reflected light for each _{n s1,} D _s2, ... D It is formed from _sn .

[0041] The reference data D _s stored in the reference data memory 35, the respective light receiving sensors 5a, 5b, 6
Each amplitude data of each transmitted light distribution or reflected light distribution corresponding to the light receiving position at a and 6b is stored.

The posture estimating unit 36 is provided with a light amount detected by the shift amount sensor 21, that is, the shift amount data memory 3.
3 has a function of calculating the lateral shift amount and the inclination of the paper sheet 1 based on the posture data of the paper sheet 1 stored in the storage unit 3.

More specifically, if the change in the amount of light detected by the shift amount sensor 21 is temporally constant outside the allowable range from the posture data stored in the shift amount data memory 33, A function of obtaining the lateral displacement amount of the paper sheet 1 from the light amount at that time, and calculating the inclination of the paper sheet 1 from the change rate of the light amount at this time if the light amount detected by the shift amount sensor 21 increases or decreases with time. have.

That is, from V = f (as) in the above equation (2), aS = f ^-1 (v)... (3), so that the lateral shift amount S is: S = (1 / a) · f ^-1 (v)… is determined by (4).

[0045] In addition, the lateral displacement in the sheet 1, and a lateral deviation of the standard of the paper sheet 1 at the time of the normal posture with no inclination to S _o,
As shown in FIG. 6, the lateral shift amount S _s at t = 0 is as follows: S _s = S _o − (1 / a) · f ⁻¹ (v) (5)

Assuming that the length of the sheet 1 in the transport direction is 1 and the lateral displacement of the end of the sheet 1 is S _e , the inclination θ of the sheet 1 is θ = tan ⁻¹ (S _e −S _s ) / l (6)

Note that the inclination θ of the sheet 1 can also be obtained by calculating the inclination of the output voltage V in FIG. 9B, that is, x / y. The reference data correction unit 37 obtains the actual scanning line position based on the lateral shift amount S and the inclination θ of the sheet 1, extracts the transmitted light amount or the reflected light amount on the reference data corresponding to this scanning line position, and It has a function of generating reference data corresponding to the class 1 posture.

The comparing section 38 and the pass / fail judging section 39 constitute judging means. The comparison unit 38 compares the reference data corrected by the reference data correction unit 37 with the actual measurement data stored in the shift amount data memory 33. The comparison is performed by, for example, one method of multivariate analysis. Mahalanobis distance D is used.

In this method, a parameter is extracted from the actually measured data and the reference data obtained from the sheet 1 such that the distance (norm) between the cluster of the good watermark and the cluster of the bad watermark is sufficiently separated. Is calculated as follows.

[0050]

(Equation 2)

As the parameters, for example, the average value μ and the standard deviation σ of the actually measured data and the reference data are used. Also, the above equation
In (7), the second matrix is the variance-covariance matrix of paper sheets, and in order to make a more reliable pass / fail judgment, prepare as many good samples as possible and determine this matrix. . By this calculation, a sample having a plurality of parameters can be compared with one numerical value.

The acceptability judging section 39 receives the Mahalanobis distance D calculated by the comparing section 38, and compares the Mahalanobis distance D with a preset threshold to judge the acceptability of the paper sheet 1. Have.

The preset threshold value is determined on the basis of a statistically permissible misjudgment rate, assuming that the inter-cluster distance between good and defective products is sufficient. Next, the operation of the apparatus configured as described above will be described.

When the sheet 1 is conveyed to the conveying line 2 at a constant speed, the sheet 1 is moved before entering the scanning optical system.
It passes between the slit light source 20 and the shift amount sensor 21, and its posture is detected.

That is, when the sheet 1 is conveyed to the conveying line 2 in a normal posture, the sheet 1 has one edge thereof at the middle of the shift amount sensor 21 as shown in FIG. The light passes through a position, that is, an intermediate position in the longitudinal direction of the belt-like light 20a.

The output voltage V of the shift amount sensor 21 at this time becomes constant at _a predetermined value Va as shown in FIG.
However, when the paper sheet 1 is conveyed with a lateral shift, the paper sheet 1 has a portion where the edge of the paper sheet 1 has an edge with respect to the shift amount sensor 21 as shown in FIG. Less.

If the sheet 1 is laterally shifted in the opposite direction, the number of edges applied to the shift amount sensor 21 of the sheet 1 increases. When the sheet 1 is conveyed with a lateral shift in this manner, the shift amount sensor 21 increases or decreases the amount of incident light in accordance with the lateral shift amount of the sheet 1, so that the output voltage V
Is, for example, the output voltage V _b is higher than the output voltage V _a normal posture as shown in FIG. (B).

When the sheet 1 is conveyed with an inclination, the sheet 1 is moved with respect to the shift amount sensor 21, for example, as shown in FIG. As such a portion is transported, it becomes smaller.

If the sheet 1 is tilted in the opposite direction, the portion of the sheet 1 where the edge of the sheet 1 extends with respect to the shift amount sensor 21 increases as the sheet is conveyed. When the sheet 1 is conveyed while being inclined in this manner, the shift amount sensor 21
Since the amount of incident light increases and decreases according to the direction of inclination of the paper sheet 1 as the paper sheet 1 is conveyed, the output voltage V increases at a constant rate, for example, as shown in FIG.

The output voltage V of the shift amount sensor 21 is
The digital data is converted by the A / D converter 32 and the main control unit 30
And stored in the shift amount data memory 33 as the posture data of the paper sheet 1.

Subsequently, when the sheet 1 is conveyed and reaches the scanning optical system, and is conveyed to the conveying line 2 at a constant speed, the sheet 1 passes below the laser oscillators 3. Each of the laser beams output from each of the laser oscillators 3 is scanned on the sheet 1. The spot shape of each of the scanned laser beams on the sheet 1 is a point, and these laser beams are transmitted through the sheet 1 and reflected by the sheet 1.

At the same time, by passing above the laser oscillator 4, each of the laser beams output from each of the laser oscillators 4 is scanned on the sheet 1. The spot shape of each of the scanned laser beams on the sheet 1 is a point, and these laser beams are transmitted through the sheet 1 and reflected by the sheet 1.

At this time, each lower light receiving sensor 5a receives each laser light output from each laser oscillator 3 and transmitted through the paper sheet 1, and outputs each electric signal corresponding to the light amount, and outputs the electric signal. Each of the upper light receiving sensors 6b receives the reflected scattered light when the paper sheet 1 is irradiated with the laser light, and outputs each electric signal corresponding to the light amount.

At the same time, each upper light receiving sensor 5a
Each laser beam output from each laser oscillator 4 and transmitted through the paper sheet 1 is received, and each electric signal corresponding to the light amount is output.
, Respectively, receives the reflected scattered light when the laser light is irradiated, and outputs each electric signal corresponding to the light amount.

These light receiving sensors 5a, 5b, 6a, 6b
Are respectively amplified by the amplifiers 8 to 11, and the A / D converter 3
In step 1, the digital data is converted into digital data, captured by the main controller 30, and stored in the measured data memory 34 as measured data (amplitude data) of the transmitted light distribution and the reflected light distribution.

When the posture data of the sheet 1 is stored in the shift amount data memory 33 as described above, the posture estimating unit 36
Is the lateral shift amount S and the inclination θ of the paper sheet 1 based on the posture data of the paper sheet 1 stored in the shift amount data memory 33.
Ask for.

[0067] That is, if the output voltage V _a posture data shown in FIG. 7 (b), the posture estimating unit 36, a change in light amount detected by the shift amount sensor 21 is within the allowable range in temporally constant It is determined that there is, and it is presumed that the paper sheet 1 is being conveyed in a normal posture.

However, if the posture data is, for example, the output voltage _Vb shown in FIG. 8B, the posture estimating unit 36 determines that the change in the amount of light detected by the shift amount sensor 21 is temporally constant outside the allowable range. Therefore, it is presumed that the paper sheet 1 is conveyed while being shifted laterally.

In this case, the attitude estimating unit 36 calculates the lateral shift amount S by calculating the above equation (4) from the light amount detected by the shift amount sensor 21. Further, if the posture data shows that the output voltage changes gradually as shown in FIG. 9 (b), for example, the posture estimating unit 36 determines that the light amount detected by the shift amount sensor 21 Since the size of the sheet 1 increases as the sheet is conveyed, it is estimated that the sheet 1 is conveyed while being inclined.

In this case, the posture estimating section 36 calculates the inclination of the change in the amount of light detected by the shift amount sensor 21 or the above equation.
By calculating (6), the inclination θ of the paper sheet 1 is obtained.
Next, the reference data correction unit 37 obtains actual scanning line positions on the paper sheet 1 based on the lateral shift amount S and the inclination θ of the paper sheet 1 obtained by the posture estimation unit 36, and Then, the amount of transmitted light or the amount of reflected light on the reference data corresponding to (1) is extracted to generate reference data corresponding to the posture of the paper sheet 1.

In this case, the reference data correction unit 37 does not correct the reference data if the posture of the sheet 1 is normal. On the other hand, if the paper sheet 1 is shifted sideways,
The reference data correction unit 37 generates reference data corresponding to the laterally shifted sheet 1 by shifting the position of the transmitted light amount distribution or the reflected light amount distribution read from the reference data according to the lateral deviation amount S of the sheet 1.

If the sheet 1 is skewed, the reference data correction unit 37 first finds the actual scanning line position on the sheet 1 based on the inclination θ of the sheet 1. Next, the reference data correction unit 37 extracts the transmitted light amount or the reflected light amount on the reference data corresponding to the actual scanning line position on the paper sheet 1, and connects the transmitted light amount or the reflected light amount to tilt the paper sheet 1 inclined. Generate reference data corresponding to.

[0073] For example, when the actual one scan line q by the slope of the paper sheet 1 as shown in FIG. 10 is scanned, the scanning lines s ₁ in a reference on the data D _s The scanning line q, s ₂ ,... S _n of amplitude data D _s1 , D _s2,.
It reads the _{q 1, q 2, q 3} ... values at which intersects the _sn, to generate the reference data Dsa corrected by connecting these _{q 1, q 2, q 3} ... each value of.

Therefore, for example, as shown in FIG. 6, reference data D _a , D _b , D _c , D _d ,... Are generated for each scanning line of the sheet 1 having the inclination. Further, if the sheet 1 is laterally shifted and inclined, the reference data correction unit 37 shifts the position of the transmitted light amount distribution or the reflected light amount distribution read from the reference data according to the lateral deviation amount S of the sheet 1, and The actual scanning line position on the paper sheet 1 is obtained based on the inclination θ of the paper sheet 1, and the transmitted light amount or the reflected light amount on the laterally shifted reference data corresponding to the actual scanning line position on the paper sheet 1 Is extracted, and reference data corresponding to the tilted paper sheet 1 is generated by connecting the transmitted light amount or the reflected light amount.

Next, the comparison section 38 is operated by the reference data correction section 37.
Data and shift amount data memory 3 corrected by
3 is read out, and the actual measurement data (the amplitude data of the transmitted light amount and the reflected light amount) is subjected to arithmetic processing to obtain characteristic parameters representing the watermark portion of the paper sheet 1, for example, the average of the amplitude. The statistic such as the value μ and the standard deviation σ is obtained.

Next, the comparing section 38 calculates the average value μ of these amplitudes.
The above formula (7) is calculated based on statistics such as the standard deviation σ, and the Mahalanobis distance D is calculated. Next, the pass / fail determination unit 39 receives the Mahalanobis distance D calculated by the comparison unit 38, and compares the Mahalanobis distance D with a preset threshold to determine pass / fail of the paper sheet 1.

As described above, in one embodiment,
Before the sheet 1 enters the scanning optical system, the sheet 1 is irradiated with the band-shaped light 20a, and a light amount corresponding to the posture of the sheet 1 is detected from the irradiated light amount to detect the light amount. 1 is obtained, the reference data is corrected based on the lateral deviation S and the inclination θ, and the transmitted light or reflection from the paper 1 when the light is scanned on the paper 1 The sheet 1 based on the actually measured data corresponding to the amount of light and the corrected reference data.
Is determined, so that even if the paper sheet 1 is conveyed with a lateral shift or inclination, the quality of the paper sheet 1 is stably determined without being affected by the lateral shift or inclination of the paper sheet 1. Thus, for example, the ability to remove defective products can be enhanced, and defective products can be removed with a high probability.

In particular, since the band-shaped light 20a is irradiated on the sheet 1 and is incident on the shift amount sensor 21, the shift amount sensor 2
1, the lateral shift amount S of the paper sheet 1 based on the change in the amount of incident light at
And the inclination θ, and furthermore, the paper sheet 1 shifted from the lateral deviation amount S and the inclination θ of the paper sheet 1
Can be generated, and as a result, the quality of the paper sheet 1 can be determined with high reliability.

Further, the scanning optical system for scanning each sheet 1 with each laser beam has a simple and simple configuration as compared with an optical system using a polygon mirror or the like, and improves the processing speed of pass / fail judgment. And cost reduction can be expected.

The present invention is not limited to the above embodiment, but may be modified as follows. For example, the light that scans the paper sheet 1 is not limited to laser light, and another light source may be used.

For detecting the lateral deviation S of the paper sheet 1, a line sensor may be arranged in a direction perpendicular to the transport direction of the paper sheet 1, or another method may be used. Further, the comparison between the reference data and the actually measured data from the sheet 1 may be performed by any means, for example, Hadamard transform.

[0082]

As described in detail above, claims 1 to 5 of the present invention.
According to 6, it is possible to provide a sheet inspection apparatus capable of accurately and stably determining the quality of a sheet even if a sheet shift occurs. or,
According to the first to sixth aspects of the present invention, even if a lateral displacement or inclination occurs in a sheet, the lateral deviation or the inclination of the sheet is corrected by reference data corresponding to the lateral deviation or the inclination of the sheet. Quality of paper sheets can be accurately determined without being affected by
It is possible to provide a paper sheet inspection apparatus capable of increasing the ability to remove defective products and removing defective products with a high probability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a paper sheet inspection apparatus according to the present invention.

FIG. 2 is a layout diagram of a slit light source and a shift amount sensor.

FIG. 3 is a characteristic diagram of an incident light amount-output voltage of a shift amount sensor.

FIG. 4 is a configuration diagram of a discrimination processing system.

FIG. 5 is a schematic diagram of reference data.

FIG. 6 is a view for explaining calculation of a lateral shift amount and a tilt amount of a paper sheet.

FIG. 7 is a diagram illustrating a conveyance position of a sheet and an output voltage of a shift amount sensor in a normal posture.

FIG. 8 is a diagram illustrating the transport position of a sheet and the output voltage of a shift amount sensor when the sheet is shifted laterally.

FIG. 9 is a diagram illustrating a conveyance position of a skewed sheet and an output voltage of a shift amount sensor.

FIG. 10 is a schematic diagram showing generation of corrected reference data.

FIG. 11 is a configuration diagram of a conventional paper sheet inspection apparatus.

FIG. 12 is a diagram illustrating paper sheets conveyed in a normal posture.

FIG. 13 is a diagram illustrating lateral displacement of paper sheets.

FIG. 14 is a diagram illustrating inclination of paper sheets.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Paper sheet, 2 ... Conveying line, 3, 4 ... Laser oscillator, 5a, 5b, 6a, 6b ... Light receiving sensor, 20 ... Slit light source, 21 ... Shift amount sensor, 30 ... Main control part, 33 ... Shift amount Data memory, 34: Actual measurement data memory, 35: Reference data memory, 36: Attitude estimation unit, 37: Reference data correction unit, 38: Comparison unit, 39: Pass / fail judgment unit

Claims (6)

[Claims] 1. A method for scanning a conveyed sheet with light,
In a sheet inspection apparatus for inspecting the quality of the sheet based on actual measurement data and reference data corresponding to the amount of transmitted light or reflected light from the sheet, the posture of the sheet being conveyed A reference data correction unit that corrects the reference data based on the posture of the sheet detected by the posture detection unit; and a reference data corrected by the reference data correction unit. Determining means for comparing the measured data with the measured data to determine the quality of the paper sheet. 2. The paper sheet inspection apparatus according to claim 1, wherein the posture detecting means is arranged at a stage preceding a scanning optical system that scans the paper sheet with light. 3. A light source for irradiating the sheet with belt-like light, and a shift amount sensor for detecting a light amount of the light amount emitted from the light source in accordance with the posture of the sheet. And posture estimating means for calculating a lateral shift amount and a tilt of the paper sheet based on the light amount detected by the shift amount sensor;
The sheet inspection apparatus according to claim 1, further comprising: 4. The attitude estimating means obtains a lateral shift amount of the sheet from the light amount at this time if a change in the light amount detected by the shift amount sensor is temporally constant outside an allowable range, 4. The paper sheet according to claim 3, further comprising a function of calculating the inclination of the paper sheet from the rate of the change in the light amount at the time when the light amount detected by the shift amount sensor increases or decreases with time. Inspection equipment. 5. A method according to claim 1, wherein one or both of a transmitted light distribution and a reflected light distribution corresponding to each scanning position when the sheet is conveyed in a normal posture is held as the reference data, and The data correction unit obtains an actual scan line position based on the lateral shift amount and the inclination of the sheet, extracts a transmitted light amount or a reflected light amount on the reference data corresponding to the scan line position, and extracts the scan light amount. The sheet inspection apparatus according to claim 1, further comprising a function of generating reference data corresponding to the posture. 6. The discrimination means calculates a Mahalanobis distance based on an average value and a standard deviation between the corrected reference data and the actual measurement data, and compares the Mahalanobis distance with a threshold to compare the Mahalanobis distance with a threshold. 2. The paper sheet inspection apparatus according to claim 1, further comprising a function of judging whether the kind is good or bad.